The Universal Mobile Telecommunications System (UMTS) is a 3rd Generation (3G) mobile telecommunications system based on the Wideband Code Division Multiple Access (WCDMA) air interface technology, and is also known as a WCDMA communication system. The structure of a UMTS is similar to that of a 2nd Generation (2G) mobile telecommunications system, and is composed of a UMTS Terrestrial Radio Access Network (UTRAN), a Core Network (CN), and User Equipment (UE).
As shown in FIG. 1, a UTRAN includes one or more Radio Network Subsystems (RNSs). An RNS includes a Radio Network Controller (RNC) and one or more base stations (Node Bs). The RNC is connected with the CN through an Iu interface, the Node B is connected with the RNC through an Iub interface, and the Node B is connected with the UE through a Uu interface. Within a UTRAN, the RNCs are interconnected through an Iur interface. The Iur interface provides connection through a direct physical connection between RNCs or a transport network. The RNC allocates and controls the radio resources of the Node B connected or related to the RNC. The Node B converts the data flows between an Iub interface and a Uu interface, and participates in radio resource management.
As shown in FIG. 2, an Iub interface protocol stack includes: a radio network control plane, a transport network control plane, and a user plane. The bearer layer involves two transmission modes: Asynchronous Transfer Mode (ATM) transmission, and Internet Protocol (IP) transmission. The voice and data of the UE are encapsulated in various Framing Protocol (FP) frames, and are transmitted at the Iub interface through the functions of the ATM or IP.
The transmission resources between the Node B and RNC are precious. Therefore, enhancing the transmission efficiency of the Iub interface and making the most of the transmission resources have been concerns of operators.
Currently, in order to save transmission resources, operators need to set a convergence device on the Iub interface link designed for converging transmission bandwidth. FIG. 3 shows the typical networking. Multiple Node B services are converged through a transmission convergence device, or converged through a hub Node B device. If multiple Node B services are converged through a hub Node B device, the hub Node B serves as a Node B, and is adapted to converge and concatenate Node B services. This networking mode is also called hub networking, and the convergence device is called a hub node. Multiple Node Bs are interconnected with the hub node. The Node B services are converged through the hub node and then connected to the RNC through an upstream port. After the services are converged through the hub node, the transmission bandwidth required between the hub node and RNC decreases drastically, and it is not necessary to plan the transmission bandwidth between the hub node and RNC according to the algebraic sum of the service bandwidths required for all Node Bs, thus decreasing the transmission expenses and increasing the revenues of the operators. For an IP RAN, the hub networking is characterized in that:
All the IP packets from the Node Bs (#1, #2, . . . , #n) to the RNC have the same destination IP address; and
all the IP packets from the RNC to all the Node Bs (#1, #2, . . . , #n) have the same source IP address.
FIG. 4 shows a router-based or switch-based service convergence networking solution. The quantity of Node Bs converged by a router or switch depends on the actual networking conditions and the location of the router or switch. At the Node B access side, 10-15 Node Bs are generally converged.
However, in the process of implementing the present invention, the inventor finds that a great average overhead of user data flows still exists on the Iub interface currently. That is because voice services are generally a majority and small packets are a majority of the IP packets between the Node B and the RNC, especially, at the early stage of the 3G services. According to the protocol stack shown in FIG. 2, in the IP transmission mode, the efficiency of encapsulating small packets is very low, and the utilization ratio of the transmission bandwidth of small packets is very low. For example, for Adaptive Multi-Rate (AMR) 12.2 Kbps services, the size of an FP frame is about 40 bytes if the Transmission Timing Interval (TTI) of the frame is 20 ms. In the case that the voice packets to be transmitted are encapsulated through a User Datagram Protocol (UDP), an IP protocol or a Medium Access Control (MAC) protocol, the overhead for encapsulation on the transport layer includes an 8-byte UDP header, a 20-byte IP header (supposing that the IPv4 protocol is applied) and an 18-byte MAC header. If the overhead for encapsulation of a voice packet with a 40-byte payload is 46 bytes, the efficiency of the transport layer is less than 50%.
Although the efficiency may be enhanced through the technologies such as IP header compression, Point-to-Point Protocol (PPP) header compression, and PPP Multiplexing (PPPmux), the router is unable to identify the destination address in the packet header correctly after compression. Therefore, such technologies for enhancing efficiency are applicable only to the point-to-point networking scenarios, and not applicable to the network constructed through Iub interfaces from multiple points (multiple Node Bs) to a single point (a single RNC). A great average overhead of user data flows still exists on the Iub interface.